The hazard items in this case are the hypergolic propellant tanks, with a chance of reaching the ground and heavily poisoning a small area. That was the issue with USA-193 [the true issue, as I'm one of the few people to insist -- well, reality is not democracy-driven]. Balanced against destruction would be hazards from some debris in higher orbit, but differential nodal regression would take such debris out of plane with the ISS within hours.

I'm not seeing any evidence the propellant has gone anywhere. It just doesn't flow out -- it has to be pressure fed from hi-pressure N2 tanks [or He?], through commanded valves. If it wasn't burned off on a mad thruster joust, it's all still there. And getting colder.

The mass ratio should be about 1.65/1.0 ox/fuel, that is nitrogen teroxide to heptyl/hydrazine.

"Most likely it is some sort of unforeseen situation related to the separation of the ship from the carrier," Alexander Ivanov, deputy chief of the Roscosmos state agency, told reporters. "It is impossible to say now who is guilty and of what."

Not to argue with you but, trackable debris from the USA-193 event was shot as high as 147 km x 2,689 km. While most of it reentered quickly, a trackable amount was sent into higher orbits. That is what would endanger ISS.

Again, this is why an similar intercept is a bad idea for ISS.

I gratefully stand corrected, and will need it more and more as time goes by, so lay on, MacDuff!

Yes, it would be a bad idea. Imagine trying to control and extinguish a fire by throwing a grenade on it.

ASAT weapons are intended for destruction of satellites. Not debris removal - it will have the opposite effect.

If the fire was in a car and the car was driving full speed toward a school, the grenade might be the best option.

I'm not saying I think hitting this Progress with a missile is the right choice, just that it's a trade-off. It adds some risk to the ISS and reduces some risk of people being hurt or property damaged on the ground. I think to really know the better decision would require running actual numbers. Plus, there's a subjective value judgement about risk to ISS versus risk to bystanders on the ground -- some might argue that it's better to risk the lives of those on the ISS who have volunteered for the program than innocent people on the ground.

Not to argue with you but, trackable debris from the USA-193 event was shot as high as 147 km x 2,689 km. While most of it reentered quickly, a trackable amount was sent into higher orbits. That is what would endanger ISS.

Again, this is why an similar intercept is a bad idea for ISS.

I gratefully stand corrected, and will need it more and more as time goes by, so lay on, MacDuff!

Yes, it would be a bad idea. Imagine trying to control and extinguish a fire by throwing a grenade on it.

ASAT weapons are intended for destruction of satellites. Not debris removal - it will have the opposite effect.

I tend to stand with this thinking. While shooting it down would likely greatly reduce risk to the ground, the amount of small pieces and other debris you would propel into higher orbits would make this counter productive. There is already way too much space debris the last thing you want to be doing is adding lots of random high energy fragments to the mix.

That being said, without a shoot-down its very likely large pieces may survive re entry, particularly since entry interface is unlikely to be controlled and the possibility of any burn being conducted prior to entry interface is very slim. So I would hope that ultimately it enters over water or a rural landmass, since otherwise it could cause some problems.

Sir Isaac Newton is in the driver seat at the moment so really it's going to fall wherever it falls.

It's already been said. ASAT weapons are designed for achieving a satellite 'mission kills'. Meaning that the objective is to simply prevent the satellite from performing its function. It just so happens that it isn't going to take a lot of physical destruction to do that. That is what ASAT weapons are for.

As has been already said they are not designed for debris removal.

Right now the situation has some thousands of variable...hitting it with an ASAT turns that into millions of variables.

Things have been reentering the atmosphere in unexpected ways since the start of the space age, apart from being more newsworthy for all the wrong reasons this will be nothing to get excited about.

Question: would there be a difference in a tumbling spacecraft reentering versus a directed path? I doubt there would be anything resembling a 'bounce' off the atmosphere, but I'm thinking it could make it more difficult to ascertain the exact (expected) point of impact?

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Remembering those who made the ultimate sacrifice for our rights & freedoms, and for those injured, visible or otherwise, in that fight.

(1) TM from 3rd stage was lost some 1.5 sec before scheduled ejection of SC;(2) SC separated more or less on time;(3) SC was found to rotate with the period of 4 seconds;(4) today, manifolds of SC were found to be depressurized which led to cancellation of the mission.

No most possible cause was named but they would check issues at the moment of separation.

Ouch. So that would mean things depressurized. Not good.

Still, seems like contrary to what I thought earlier that the problem was with the 3rd stage after all.

Does the fuel manifold pressurize before or after separation? It still looks as if something popped during the pressurization event.

Question: would there be a difference in a tumbling spacecraft reentering versus a directed path? I doubt there would be anything resembling a 'bounce' off the atmosphere, but I'm thinking it could make it more difficult to ascertain the exact (expected) point of impact?

When Mir was deorbited it was put into a spin to help it break up completely. So if anything the tumbling will make less (if any) debris reach the ground. I'm not sure if the tumbling would make predicting the reentry location more or less difficult. If I had to guess I'd say it wouldn't matter, but I'm nothing close to an expert.

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There are so many variables on satellite decay that it is next to impossible to get an accurate reentry prediction time with large error bars less than 24hrs in advance, and an estimated reentry location with large error bars less than a couple of orbits in advances.

It's already been said. ASAT weapons are designed for achieving a satellite 'mission kills'. Meaning that the objective is to simply prevent the satellite from performing its function. It just so happens that it isn't going to take a lot of physical destruction to do that. That is what ASAT weapons are for.

What they were designed for doesn't really matter. All that matters is the effect they would have in this case. And, in this case, it is likely they would break Progress apart -- the frozen mass of propellant in particular -- and decrease the risk to people on the ground.

This is *not* an issue of debris removal. Why do people keep talking as if an ASAT system would be used for debris removal?

This is a case of debris that is already going to be removed naturally. The only question is whether or not to turn it from one big piece of debris into lots of little pieces of debris right as it starts to really enter the atmosphere.

Some of the little pieces might temporarily go higher for a few orbits, but it's simply not possible to create long-lasting debris from an ASAT hit like this. It's simple orbital mechanics. Since the ASAT hit would be so low in the atmosphere there there is significant drag there, all debris created would have a perigee no higher than that altitude. It might have a high apogee initially, but with a perigee so low, the orbit would quickly decay.

Things have been reentering the atmosphere in unexpected ways since the start of the space age, apart from being more newsworthy for all the wrong reasons this will be nothing to get excited about.

That's no reason not to do something about it if we can and if we determine it makes sense.

Again, as I said in another post, I'm not claiming that an ASAT hit would be the best choice. What I am claiming is that it's a trade-off, and one must run detailed numeric calculations to decide which is better. Anyone claiming the answer can be determined without running the numbers is wrong, in my opinion.

Of course, as others have said, there are political and legal issues as well. Obviously, the U.S. doesn't have the right to make the decision. Russia has the right to make the decision. But that doesn't stop us from considering what the right decision would be for Russia to make.

There are so many variables on satellite decay that it is next to impossible to get an accurate reentry prediction time with large error bars less than 24hrs in advance, and an estimated reentry location with large error bars less than a couple of orbits in advances.

Even much closer to it's tough. I remember watching the UARS end of mission webcast and even with live telemetry data in the hours before reentry the guesses were only as precise as "probably in the next two or three orbits."

I would ask that further discussion on removing Progress from orbit using means other than normal orbital decay should be either redirected into a new article or dropped--especially the remarkably silly idea of using military applications to remove it.

There are thousands of objects in space, many are satellites, pieces of them, junk from their launch vehicles, or stages themselves. Some are as heavy or heavier than Progress, and some have denser qualities where survival of some pieces from destructive re-entry is likely. Does anyone remember Skylab's more or less uncontrolled reentry in 1979? And that was at least 20 many times larger.

Yet we only hear of a land impact of any of these pieces very rarely. Progress is designed to destroy itself by reentry. The only thing that's different now is that it likely won't enjoy a controlled deorbit over the ocean, but this is no less different from long-deactivated satellites or other space junk. Earth's atmosphere is a great protector; even iron meteoroids don't get through without a fight. Progress will fare no worse than its siblings.

.... Things have been reentering the atmosphere in unexpected ways since the start of the space age, apart from being more newsworthy for all the wrong reasons this will be nothing to get excited about.

Uh, no. Objects of this size and larger [especially those with large quantities of toxic chemicals] have for decades usually been actively, deliberately steered into South Pacific impact zones, BECAUSE of the unacceptably large risk of random fall. See http://www.thenewatlantis.com/publications/down-in-flames

Back to the mission itself. I've been mulling it over and just cannot imagine any energetic event at payload insertion that would result in an accidental asymmetric force on the Progress sufficient to induce such a fast tumble rate -- except a LONG thruster burn. That would itself take up lots of propellant, even more if other thrusters were commanded on to attempt to counteract it.

What are the alternative sources of sufficient rotational force on the Progress?

Back to the mission itself. I've been mulling it over and just cannot imagine any energetic event at payload insertion that would result in an accidental asymmetric force on the Progress sufficient to induce such a fast tumble rate -- except a LONG thruster burn. That would itself take up lots of propellant, even more if other thrusters were commanded on to attempt to counteract it.

What are the alternative sources of sufficient rotational force on the Progress?

One possibility is a rupture of a prop tank on Progress, either because of something internal or because of strain from a hit from the upper stage after separation.

Another possibility is that Progress separated, moved some distance away, then was hit by the upper stage after it had moved off the axis of the stage but before it was entirely clear of its path.

And another possibility is that the spin was caused by incorrect firing of Progress's thrusters. If the sensors were feeding bad data to the computer, it might have fired the thrusters when it shouldn't have.

Or, the thrusters might have been wired up wrong. When the computer thought it was firing one thruster, it actually fired a different one, then kept firing it to try to correct the error.

What about the possibility that perhaps Progress didn't separate from the third stage at all initially, and the third stage then did it's standard post-launch prop purge/spin maneuver with the Progress still attached, following which Progress separated due to G forces and subsequently exhausted all it's propellant trying to null out the spin rate.